I’ve often referred to the differing fates of the Austin neighborhood on the far West Side of Chicago (where my wife grew up in the 1960s) and the adjoining suburb of Oak Park (where my father grew up in the 1920s). In the 1970s the city of Oak Park imposed a covert “black-a-block” racial quota to prevent the white flight that has left Austin post-apocalyptic-looking. Here’s a New York Timesdot map of 2010 Census data that shows how effective the city fathers were at stopping complete ghettoization along Austin Blvd., the municipal boundary.